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Hey folks check and make sure your engines are propped right and turn the proper WOT.

Don't depend on the manufacturer, the boat dealer, the engine dealer, your dash tachs. Take it upon yourself to be sure.

It was an expensive lesson for one guy down here.

After 6 service places before me and one engine change, I replaced the second original diesel in this guys boat.

After wondering for about 1/2 second why he lost both engines 2 years apart I decided to check the prop size.

Bingo 2" over pitched.

There's a reason an engine blows pistons and rods after only 700 hours.

Ask questions if your mechanic doesn't. Apparently nobody before me either gave a crap or was too stupid to even put 2 and 2 together.

After asking if the owner had the original delivery sheet, which he did, it clearly states delivered with 19x25 4 blade props on 300hp 2.0:1 3950 rpm diesels.

Sorry but you don't need a prop program to figure that one out.

Rampage I'm sure is going to be getting a legal paper from an attorney very soon I predict.

Bruce-

Should the engines turn up over spec RPM. I am being told my 2800 RPM engines should turn up 2900?

-Andy

You would think somebody would have checked.

ok, so it came from the factory with the wrong wheels?

Came from the factory with the wrong wheels, boat dealer didn't catch it and 5 previous service centers didn't catch it.

Everyone down the line should have known better, period.

As far as engine WOT rpm, always follow factory recommended limits.

If a dealer is telling you something different than factory guidelines, check with the factory before doing anything.

And if your getting somebody at the factory who seems no sharper than a 4' tree stump, make sure anything you get is in writing with factory letter head so the liability rest square on the engine maker.

Some people might jest at my no sharper than comment but take it from someone who talks to factory techs, designers and engineers all the time, you wonder how most ever got past the sixth grade.

Ok Bruce. Very good advice.

I'll bite...

What should my 240 hp, 4 banger Yanmars turn up to at WOT?

D

Dug: Yanmar recommends a mininum WOT of a fully loaded boat to be 3450 rpm. As far as cruise rpm, there are different opinions. I choose to cruise a 2750 -2800. Some say 3100 won't hurt them if you can get 3450 wide open. But if something goes wrong at the higher rpm, you may not have enough time to respond before a meltdown.

Eddy G.

I prop mine for 3450 and run at 3100 all of the time (90%) that I'm not running at 3300 (10%).

Ok, I think I run at a higher rpm at wot. Like 35-3700. I cruise at 3100.

That gives me a 27-29 knot top end, and a 23 knot cruise.

Bruce wrote:Some people might jest at my no sharper than comment but take it from someone who talks to factory techs, designers and engineers all the time, you wonder how most ever got past the sixth grade

Not unique to just the marine world.......

Harry

Brewster Minton wrote:You would think somebody would have checked.

Maybe if they cared...


Some years ago we get a pair of wheels from a dealer we work with. They tell us the boat has a vibration and the client refused to take delivery, please check the wheels. So we send them out and find out one is a bit out of balance and is marked incorrectly, its not 40 square but 40 x 38". Dealer says to square it up and balance.

Now the boat has less of a vibration, but that engine won't turn full RPMs and client will not accept boat. Long story short the boat had some motor problems. We figure the factory had a problem with the motor and repitched the wheels to gain the lost RPM's.

Some boat manufactures and brokers have been notorious for knowingly over propping their boats. The whole thing is speed... They tout their boats to run at X speed, when in reality, if properly propped, there would no way they would run that fast. In those cases, it's all about greed and speed, owner be damned, make the sell and we're outa' here.

Just to jump into the frey. Mike and Doug what engines,gears and props are you running? I have 454s w/1.5to1 gears w/ 18x18 wheels. At 2800 rpm I am running a steady 22nts. But my wot is only 3600. My carbs go to all 4s at 3200. What does one think? All thoughts considered.
Chris

Chris- do you know what the specs for those engines are as far as rpm's go?
3600 for a gasser sounds low so you MAY be a bit overpropped.

Walter; Not sure they are 98s 454/330hp They should turn 4500 or up to 5500 w/ no prob. I am thinking like a car person at this point. Bottom is clean w/ very little load. Next time out I will write down some #s rpm etc
Thanks Chris

I'll add another factor to consider - underwater drag. Prior to AJ being damaged in Katrina, she cruised at 24.5 kts at 2400 RPM (250 6BTA Cummins, 1.5 gears, 21x22 three blade Nibrals, no cup) regardless of load and easily made 2650 WOT, 50 above the rated 2600. Underpropped if anything as she jumps from idle to WOT in 7-8 seconds.

Both struts were cracked in Katrina and the only replacements we could find were the huge beefy ones from Danny at Hi Tide. Capt. Patrick said to grind the leading edge down but we did not have time - remember, I'm in a mostly destroyed boatyard in New Orleans trying almost a year after the storm to get the hell outta town....anyway, with clean bottom and props reworked she dropped to 23.5 kts at 2400 and still made the 2650 WOT with ease....the struts cost me a knot...

New piece of the puzzle is recently I put new shaft and rudder zincs on, and used the large "do-nut" style shaft zincs because that's all Hamilton Marine had at the time and I was in a hurry. Andre' helped me install them using his lift and we both commented how big they were vs. the usual teardrop shaped ones....well, they cost me about another 3/4 kt at 2400 and I'm still getting 2650 WOT with ease....the bottom is slimy, but she's in fresh water and no barnacles and the props and Capt. Parick's stainless oversize rudders are spotless.

So the combination of oversize struts and do-nut shaft zincs seem to have cost me close to 2 kts....with no decrease in RPM so it has to be increased underwater drag. She still jumps on the step like she always does, idle to WOT in 7-8 seconds regardless of load.

So do you guys think I've increased the "load" on the engines, or is the increased drag causing some prop slippage?

UV

Chris wrote:I have 454s w/1.5to1 gears w/ 18x18 wheels. At 2800 rpm I am running a steady 22nts. But my wot is only 3600. My carbs go to all 4s at 3200. What does one think? All thoughts considered.
Chris

Before I reduced DeNada to a pile of rubble she was powered with a pair of 454 and I have never been real sure of the horse power. The engines were Marine Power carburated.....I gustimate 300/325 hp.

They were outfitted with Velvet Drive gears 1-1/2:1
My wheels were 18x17 3 blade and I specifically rememeber that at 2900 RPM we were making 19 knots GPS speed.

WAO she would turn 4700 and I believe the top speed was 29 knots.


As far as the diesels go, especially the Cummins, I have a question......are the pumps/governor setup to allow the engine to exceed its rated speed?

Vic is saying that AJ's engines are rated at 2600 but will turn 2650......I have others make similar statments.

In my Detroit Diesel days the governors were set at rated RPM. It was always our rule of thumb that the engine should turn the rated RPM no load WOT and in gear it should turn 50 RPM less than NO LOAD speed......seen hundreds of them setup that way.

Harry

So do you guys think I've increased the "load" on the engines, or is the increased drag causing some prop slippage?

Your loading is fine Vic, you just got too much dead metal in the water... Also, in relation to the shaft zincs; rotational drag is greater than linear drag. When a shaft is turning in the water, the water is literally spiraling around the shaft, therefore holding the surface of the shaft longer than it would sliding beneath the hull. Those donut style zincs are greatly adding to the rotational drag.

Otherwise, you're fine. The next time you're on the hill, have the yard pull the shafts and bullet down both ends of the strut tubes and install the normal shaft zincs. You'll get nearly all of your lost speed back.

Vic- Under no-load (at the dock and in neutral) can you run her up to 2800 rpm's? I discovered my engines had governors on them that did not allow me to run beyond 2650 load or no load. I kept adding pitch and cupping to my props and still always wot'd at 2650 which I thought was weird, yet the boat kept increasing speed with each new prop adjustment. I finally questioned this with a Cummins mechanic who was working at the dock and he clipped the governors off and lo and behold I wot'd under load at 2750 with the props I presently have, which means I am still underpropped by about an inch of pitch. The point I'm making is that if you do have governors set at 2650, you can add these water resistant items and you probably will always hit that number because the boat cannot exceed it. Absolutely the donuts rather than the torpedo shaped zincs and your heavy duty struts have slowed you down a bit (temporarily). Strangely, in my case, I have also found an improvement in fuel consumption since we removed the governors. My last fill up got me 1.8 nmpg. Walter

I have only used donut shaft zincs over the years. Drawing a blank as to what the other ones look like. Is it fair to say removing the donut zincs and reducing the rotational drag would give my boat extra speed. I think I might try it this weekend. Time to replace the shaft zincs anyways.

On another note, My cruise speed at 3300 RPM is always 22 knots. My WOT RPM seems to vary from trip to trip. Usually close but noticable variation. Full water tank changing wetted surfaceof hull? Should I be changing fuel filters more often? So much to learn, so little time!

The shaft zincs we use are sort of football shaped, tapered front and back. After tightening the set screws with your allen wrench, give each side a sharp rap with a hammer and you'll find you can tighten them up a bit more.

chris pague wrote:Just to jump into the frey. Mike what engines,gears and props are you running? Chris

Yanmar 230 HP 4bangers, 2:1 gears and either 20X22X4 blade (slower and smoother) or 21X23X3 blade (faster but not as nice of a wake patern at 7.5 knots).

UV,
If your turning rated WOT your fine it looks like.

Diesels have a certain amount of loading leeway when set up properly.

Certainly the trips from the fish camp or Venice to PE is a testament to that.

You can lose speed thru drag and your burning a bit more fuel than you would but keep the same rpm at WOT. It may be though that your normal handle position for your cruise range is slightly further than before.

Don't underestimate the scum on the bottom and over comming the surface tension of that.

What this all boils down to is trying to get around a fat woman at an all you can eat buffet. It's possible but it will take more effort and fuel usage.

chris pague wrote:Just to jump into the frey. Mike and Doug what engines,gears and props are you running? I have 454s w/1.5to1 gears w/ 18x18 wheels. At 2800 rpm I am running a steady 22nts. But my wot is only 3600. My carbs go to all 4s at 3200. What does one think? All thoughts considered.
Chris

If you are only getting 3600 rpm and your telling me you should be able to turn 4500 or more under load, then

Your over propped.


You need to be able to attain the WOT RPM stated in your manual with a clean bottom and loaded up. I have heard some 454's will run higher WOT RPM's then others, but it is usually stated in the manual or call the factory / dealer for that spec.

The way I explain it to people "it's like riding a 10 speed bike, in 10th gear only. Sure you can go faster but it's murder when going up hill...boats are always going uphill when cruising.



It could also be attributed to tachs being off, alignment's out, wheels out, drag from debris ( barnacles, growth, bags, etc.) engines not running correctly. BUT, if both engines are cranking the same 3600 WOT I find it hard to believe you would have a matching set of problems to give identical readings.

I think my 454s (and most non-HO marine 454s) are supposed to go to 4200-4400 WOT. As they've gotten tired, they can't get there anymore. Along with that has come the secondaries opening closer to 3000 than 3200 like they used to. I had the same set-up as Chris has, but on a FBC with an enclosure, and years ago she'd run up to 4200 and over 30 knots. At 2800, where I run her now, I get close to 20 knots. I now have 17x15 4-blades with #5 cup--I had 18x18 3-blades.

Chris--Your motors should run up higher than 3600. The propping sounds fine. I'd look at the tune of the motors. Make sure everything is fully opening up.

John you may be correct. Tho the engines run fine and start right up. Timeing has not been checked in a while. Bottom may have some scum etc. I do not like to run much over 3gr I may create to much foame in my beer can? What advantage do feel you get out of the 4 blades?
Chris

Woops, Just got off my duff and started looking for the simple shit. Guess what? Controls are loose and not opening the trottles all the way. Time for a boat ride will get back to all later?
Chris

Chris-

Not opening up is an easy fix--wish mine were so simple. I got the 4-blades off of Dug when he repowered to have a spare set of wheels and try 4-blades. For my use (Chesapeake Bay) and my application (gassers) I don't notice any difference. Really glad your fix is something that should be simple and cheap.

John

Thanks guy, that's what I figured. Walter, my Cummins turn up 2900+ WOT with no load as always.

UV

I found the 4 blade wheels to be smoother.

I changed too many thing to know about the performance end. I wound up cruising a bit faster ( 1-2mph ), but that could be because I went to a larger wheel when I introduced reduction to the drive train.

On Sr's boat he gained about a knot or two at cruise and it runs a good deal smoother. His issue was the butt always squatted and the 4 blades gave the stern some needed lift.

My 3208T (320hp) only turns 2500 rpms....rated for 2800. I put a one inch diameter smaller wheel on (the regular wheel had a bent blade, I needed to get underway, wasn't worried about being underwheeled) and it ran right up- to 2500!!! Is this engine governed? I don't see any other explanation for it not turning higher rpms with a smaller wheel.

The engine is on it's second rebuild since new, the previous owners had always run it at 2000 rpms for 20 kts of speed. No problems. I lost 2 kta @ cruise, and 1 1/2 kts @ troll (idle).

Any thoughts??

Steve- As far as a governor goes, I am unfamiliar with the setup on your engine. Look at your injector pump and where your throttle cable connects to it. On the Cummins it's a wire with a lead seal that prevents the throttle setscrew from going beyond were the wire stops it. A wire cutter allows you to turn the setscrew further, but I would check with your engine's manufacturer as to what your no-load max rpm should be. Hope I've helped. Walter

chris pague wrote:Just to jump into the frey. Mike and Doug what engines,gears and props are you running? I have 454s w/1.5to1 gears w/ 18x18 wheels. At 2800 rpm I am running a steady 22nts. But my wot is only 3600. My carbs go to all 4s at 3200. What does one think? All thoughts considered.

Chris,
I was getting 4200 Starboard and 4400 on the port engine. Port engine still good, starboard is the one that died. 1.56:1 gears. Turning 18x18 3 blade Nibrals (no cup). 30 knots at WOT. Cruised at 2800 rpm for 22-23 knots. Secondaries also kicked in around 3200.

Steve,
It could very well be that during the rebuild the stop adjustment was turned back.

Also make sure your tachs are accurate to the actual engine rpm to be sure.

A good check is neutral no load rpm check.

3000 to 3150. If you can't achieve that you'll never achieve loaded rpm.

If you get no load then I would have your prop shop do a check with the props size you have vs what you should have.

If that is okay, then look at engine.

Unless that engine was mistreated, overheated or had in excess of 15,000 hours theres a reason it has had to be rebuilt twice. It could be prop load.

Thanks Bruce.......
The boat is a '72, that's why one engine rebuild. The second was due to incorrect winterization two owners ago. I now have around 1200 hours on her. I assumed the engine wouldn't turn above 2500 to the throttle linkage hitting the engine, so I was surprised when the small wheel also got only 2500. This made me think "governor". I'll have to try the no load idle revs. I suppose if it won't go too high, that there may be a governor. I don't think it's a commercial engine; the specs say 320 hp @ 2800 rpms. Interesting.

If that's what the specs say, then it MUST no load at 3000-3150 or you'd never be able to properly figure out how to prop her. That was my problem (reverse of yours). I kept adding pitch every season and still hitting my 2650 wot. After adding 2" and cupping, I knew something was screwy. If your linkage/adjustment screw is hitting your engine right now at it's max position and you're still hitting 2500 wot on no-load, try removing the cable linkage and going full throttle manually. If you increase no load rpm by doing that, you may have found your problem. A slight repositioning of your injector pump or linkage arm are possible solutions as they may have become your governor as they presently are.

Walter,
I would agree BUT for the engine only turning 2500 w/ a much smaller wheel on the boat. It now revs up much faster, but only to 2500. Smaller wheel, more revs, right?

I will be interested to see the no load revs. Will do it as soon as the monsoon is over. :)

It may want to go to higher rpm's but can't because that throttle arm is maxed out against the engine. The test will be the no-load max rpm. If it's only 2500 rpm, disconnect the arm from the cable if you think it will advance further manually and do it that way. If there's a setscrew that stops it, see if you can adjust it to give you more throw. If that setscrew is blocked or wired down, THAT's your governor.

As Walter pointed out make sure the throttle hits the stop on WOT.

I sometimes take that for granted as everyone should check that first.

I've got 3208's with over 20,000 hours with no rebuilds in commercial apps.

Care not time is the factor.